1. Field of the Invention
The invention relates to a scroll fluid machine such as an air compressor, a vacuum pump, a refrigerant gas compressor, a compressor for an oxygen inhaler, and an expander for energy collection and temperature difference power generation.
2. Description of the Related Art
The scroll fluid machine as disclosed in Japanese Patent No. 3540244 includes an eccentric shaft inserted into an eccentric hole formed in a rotary shaft to penetrate therethrough via a bearing, and an anti-self rotation mechanism for preventing self-rotation of the eccentric shaft. The anti-self rotation mechanism for the eccentric shaft includes a frame-like support member fixed to a casing, and a movable plate slidably supported on the support member, which has a long hole along a longitudinal direction orthogonal to the sliding direction. Cutout surfaces are formed at both ends of the eccentric shaft so as to be engaged with the longitudinal surface of the hole.
It is difficult for the aforementioned related art to reduce the width of the movable plate in the direction orthogonal to the sliding direction, and further to increase the length in the same direction as the sliding direction. In other words, it is difficult to increase the length of the movable plate, and accordingly, the large key load resulting from the self-rotational torque is likely to cause galling and wear of the sliding portion. As it is difficult to reduce the width of the movable plate, imbalance between the left and right sliding resistance values may cause the moment to rotate the movable plate. It is difficult for the movable plate to smoothly slide, resulting in unsteady sliding operation. It is difficult to increase the length of the cutout surface at the end of the eccentric shaft in the sliding direction, which makes the key load resulting from the self-rotational torque excessive, resulting in galling and wear. As the rotating angle defined by the gap between the key and the key groove becomes large, it is difficult to accurately maintain the wrap phase between the fixed scroll and the orbiting scroll. This may cause the noise and galling owing to the wrap contact, resulting in deteriorated performance.